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Thread: Girvin fork

  1. #1
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    Girvin fork

    Who was looking for a Girvin fork? One of my riding buddies was joking about having one "for sale" and really does. I'm sure you've got it by now for whatever project it is, but I know it was someone on here that needed one. If you still do, I have lines on a couple it sounds like.

    Later,
    Jay

  2. #2
    pvd
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    One of the worst forks ever before the DUC.

    I used to call those forks 'StapleGuns'. Many of the itterations had no provisions at all for rebound damping. Litterally dangerous at any speed. Other than that, they had no tortional stiffness to speak of.

  3. #3
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    Quote Originally Posted by pvd
    One of the worst forks ever before the DUC.
    Nice! Good to see your sense of humor is turned on today, Peter.

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    Walt was looking for one

  5. #5
    pvd
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    I gotta admit, the Shiver SC was amazingly bad as well. I dealt with that for too long before giving up.

  6. #6
    Relax. I'm a pro.
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    The linkage fork? We used to ride bikes with those forks at full speed into curbs. They were kind of fun for that.

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    I'm feeling PVD on this one. Girvin.. everything Girvin is shite. Unreal stomach turning, projectile vomit bad. Look at the dude.... bad bad bad. The only site I could find a pic of him is:

    suwonalpha.co.kr

    And google told me I would die if I opened the link.

    Bad.

    -Schmitty-

  8. #8
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    That was me.

    Yes, it's a stupid idea, but I am thinking of building a "modern" version of the Girvin/Noleen/K2/whatever linkage fork. I wanted a garbage one in hand to mess around with.

    Reason? I need a stupid winter project, I hate brake dive, and I think the fork could be improved with bearings instead of bushings and a 20mm axle. Not to mention an RP23 instead of gnarly elastomers.

    I'll probably end up with something even crappier than the original. But hopefully it'll be fun. So Jay, if your pal wants to *give* me a fork, great. I'm not going to pay money for one, though, considering that I really only want it to help solidify my thoughts on how to go about building my own. 1 1/8" would be preferable, in the case that I actually wanted to ride around on it at any point, but it's not necessary.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

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    Should be a good exercise in machining!

    Replacing the many bushings with bearings will drive weight through the roof.. both from the bearings themselves and the needed thickness on the linkages to accomodate the bearings.. it will get very wide as well for the same reasons.

    Try to use needle bearings it seems...

    I think I just saw one in the bone pile in a shop here.. I'll let you know.


    -Schmitty-

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    Yup!

    I'm aware that the weight will be, um, heavy. That's not particularly a concern for me, though - I regularly ride a 40 pound DH bike on XC rides, and I have no interest in selling this thing to anyone.

    I'm not a great machinist and not good with computer-aided drawing/design, so I thought this would be a fun project for me to work on those skills. That's the main idea, really.

    My initial thought was to recess the bearings (well, 4 sets of them, anyway) in the fork legs to keep things from getting too crazy wide, but I'm really only at the random idea stage right now. Hence my interest in an old fork to play with.

    -Walt


    Quote Originally Posted by Schmitty
    Should be a good exercise in machining!

    Replacing the many bushings with bearings will drive weight through the roof.. both from the bearings themselves and the needed thickness on the linkages to accomodate the bearings.. it will get very wide as well for the same reasons.

    Try to use needle bearings it seems...

    I think I just saw one in the bone pile in a shop here.. I'll let you know.


    -Schmitty-
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

  11. #11
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    I think there is absolutely no reason why a linkage fork couldn't be viable with modern technology (Just ignoring that German A fork for a second). In fact, think of the three main components - legs and two swing links - perfect for composite construction.

    Walt, this is a cracker of a project and one I've been daydreaming about for years.

    I say just ignore the Girvin and do one from scratch out of steel. Use a Turner Igus bushing kit as your pivots, grab a Fox RP23 and go for it!
    No longer member of the bike industry nor society, so don't hassle me.

  12. #12
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    I had the coil version on my 857. I quite liked it, actually. Stiff and responsive (for the time, perhaps it wouldn't be great by today's standards). The older elastomer versions were pretty bad, though. I'd be curious to see a modernized 29er version of this.
    WTB: Niner SIR9, size L, first gen
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  13. #13
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    Yeah...

    I'm not planning to *use* the fork for anything. I just want one to play with (and see how they did what they did) because I've never really looked at one closely. From everything I've heard, they sucked pretty badly in terms of damping and lateral/torsional stiffness. I think some bearings and a thru-axle might solve the latter two issues, and an rp23 (or whatever modern shock) would certainly help with the first.

    I'm guessing that with nice composite/alloy construction, you could make a ~4# fork that worked pretty darn well. I could be wrong, and I'm sure that what *I* build will be at least a pound heavier than that and possibly quite crappy. But as I said, I like goofy projects. I'm glad *someone* doesn't think I'm an idiot...

    Does Turner sell the bushing kit you're referring to? I was sort of looking at doing bearings, but I'm not married to anything at this point.

    -Walt

    Quote Originally Posted by Thylacine
    I think there is absolutely no reason why a linkage fork couldn't be viable with modern technology (Just ignoring that German A fork for a second). In fact, think of the three main components - legs and two swing links - perfect for composite construction.

    Walt, this is a cracker of a project and one I've been daydreaming about for years.

    I say just ignore the Girvin and do one from scratch out of steel. Use a Turner Igus bushing kit as your pivots, grab a Fox RP23 and go for it!
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

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    Just some background...

    Just as explanation - I've never ridden a mountain bike linkage fork, but I come (sort of) from a motorcycle background (mostly enduros). I used to borrow a friend's 1100gs (a BMW street/touring bike which had a linkage type front suspension setup) and just be *amazed* how much better the bike handled in any kind of braking situation. I never got around to trying out a linkage setup on a mountain bike (and in fact I'm pretty much a rigid bike dude now) but I always wondered about it. So there it is.

    -Walt
    Waltworks Custom Bicycles
    Park City, UT USA
    www.waltworks.com
    waltworks.blogspot.com

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    Hey Walt, give me a history lesson here: wasn't the Girvin designed by the brother or some relation to Kevin Hines (the national enduro champ years ago) or was that Pro-Flex? I have a lengthy enduro past as well.

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    Yeah, you can buy bushing kits straight from Turner. Nice, easy, lightweight solution.

    This would be a great little fun project. You could make the linkages from formed laser-cut sheet, turn the bushing seats from tube.....legs would be simple.

    Awesome.
    No longer member of the bike industry nor society, so don't hassle me.

  17. #17
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    Check the WW forum.

    Quote Originally Posted by jay_ntwr
    Who was looking for a Girvin fork? One of my riding buddies was joking about having one "for sale" and really does. I'm sure you've got it by now for whatever project it is, but I know it was someone on here that needed one. If you still do, I have lines on a couple it sounds like.

    Later,
    Jay

    IIRC, there was some guy who slapped a Fox Float in a Look linkage fork (a clone of this fork made of carbon, I think) and he said it was actually pretty good. Not sure how much I believe it. Those fork legs look like they would allow a ton of twist flex to me.

  18. #18
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    I have a parafork and they are stiff and responsive and handle fine at low speeds. I had a bad crash and I don't know what happened, I just lost it plowing into sand (nothing I haven't done before), I blame the fork. I haven't used it since, I just don't trust it.

  19. #19
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    I loved my old Amp linkage fork, never had any issues with it, I have been eyeing up the German linkage fork although the fact the linkage points forward not back like the Amp does look a little odd.

    Go for it mate I think it will be a fantastic project, Linkage forks can be great no stiction, light weight and the ability to play with the axle path

  20. #20
    PMK
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    Quote Originally Posted by moto367
    Hey Walt, give me a history lesson here: wasn't the Girvin designed by the brother or some relation to Kevin Hines (the national enduro champ years ago) or was that Pro-Flex? I have a lengthy enduro past as well.
    Yes, when Pro-Flex was in Rhode Island, Kevins brother was part of the crew.

    PK

  21. #21
    PMK
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    All the discussion about using Turner bushings, these as mentioned are from IGUS.

    If my memory is correct, the Girvins used IGUS bushings also.

    I owned and rode and 853 ProFlex with the Girvin fork back in 93. By todays standards it was very flexible. Compared to the forks of the era like the Manitou 4 and RS Mag 21, I don't recall it being much stiffer nor softer in torsional movements.

    I too have been deciding on building a new fork. Since the majority of our riding now is all tandems, the fork situation and performance is pretty slim pickins.

    Currently our Cannondale MTB tandem has a Moto Freeride. Yes stiff but maintenance intensive with no new parts available. Plus these things are prone to cracking triple clamps, and tough to get enough spring rate for the tandem.

    So I've been contemplating building a leading link style fork similar to that used in sidecar motocross racing. The tandem can not float or lift the front wheel, so every thing passing beneath the tire is basically an uncontrolled impact.

    My thoughts for a leading link is more based on terrain following ability first, rigidity can be designed in as weight is not a primary concern, but somewhat important.

    Rather than the more common two damper design, I planned to use the typical swingarm and vertical leg structure, but run a second set of verticals into a link driving a single damper. This second link would be similar to the Lawill leader type design. The swing link would dial in the leverage ratio and I'd hopefully stuff any quality 6.5" rear damper in there. This second link I'm hoping would compliment the side to side rigidity, this may allow building a slightly lighter swingarm.

    At the moment, and until I draw it on the computer coupled to a drawn frame, my greatest concern is toe clearance for the swingarms rear loop.

    Crazy or not, any thoughts.

    PK

  22. #22
    pvd
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    Quote Originally Posted by Walt
    I used to borrow a friend's 1100gs (a BMW street/touring bike which had a linkage type front suspension setup) and just be *amazed* how much better the bike handled in any kind of braking situation.
    That's Telelever. It's still basically a telescoping fork, but the spring and damping is not inside the tubes. The link to the extermal shock allows the fork to get a maximum amount of support during braking. It's a very good idea. It has honest advantages for tuning and in structure. I've seen somebody doing it on bicycles. I'll need to find that.

    Nothing can elliminate brake dive since the physics dictate that more weight goes to the front during braking. Any system that minimizes dive is basically shutting the fork off at a time when it's needed the most to maintain traction. Motorcycles gave up on this concept about 25 years ago.




  23. #23
    pvd
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    http://en.wikipedia.org/wiki/Motorcycle_fork

    Actually, that bicycle was a Duolever configuration. I think that this would be a much better direction for you to go.



    Whyte PRST-1



    Whyte PRST-4

    You may want to give them a call. http://www.whytebikes.com

  24. #24
    pvd
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    Here's the page of the system designer, Hossack.

    http://www.hossack-design.co.uk

  25. #25
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    Quote Originally Posted by pvd
    . I've seen somebody doing it on bicycles. I'll need to find that.
    This it?

    -Schmitty-
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